Process of manufacture of alkali metal cyanid



APPLICATION FlLED|r1ARI6.19l8.

Patent ATTORNEY FLOYD J. METZGER, 0F NEW YORK, N. yY.

PROCESS 0F MANUFACTURE 0F ALKALI METAL CYNID.

Specicaton of Letters Patent.

Application led March 16, 1918. Serial No. 222,812.

To all whom z'zf may cof/wem Be it known that I, FLOYD J. Mnrzcnn, a citizen of the United States, residing in the city and county of New York, State of New York, have` invented certain new and useful Improvements in Processes of Manufacture of Alkali Metal Cyanid, of which the following is a specification.

The present invention relates to the production of alkali metal cyanids, and more particularly, to a process adapted for use in the production of such cyanids from the customary mixtures of ingredients making up the furnace charge, that is to say, from mixtures of alkali metal carbonates or alkali metal hydroxids (or both), together with coke, charcoal, or equivalent carbonaceous a material, and with or without the addition of catalytic material such as iron, the operation being conducted at an elevated temperatureand in the presence of nitrogen or a nitrogen-containing gas.

Wh'le the vreactions involved in this generalprocedure are well known, various practical-@difficulties have been encountered in vsuch endeavors as have been heretofore made to introduce the process into commercial use. For instance, in order to bring about the fixation of the nitrogen Vfor the production of cyanid in such processes, it is necessary,

`as above indicated, to maintain a high temperature (approximately 8500 C.-1000 C.) which, of itself, introduces complications in the construction and maintenance of the apparatus employed. So also, at the temperature necessary for reaction, the alkali metal carbonate or hydroxid (or both), are in a molten or semi-fluid condition, so that the entire furnace charge is more or less plastic, in which state it opposes serious obstacles to the well-distributed contactbetween the nitrogen gas and the furnace charge, necessary lfor an efficient and uniform procedure.

Heretofore, the endeavor to realize an industrial utilization of the general process has encountered the notable obstacles that the semi-plastic charge adheres, to a large extent, to the inner walls of the furnace, in the absence of any provision for preventing such adhesion. To meet this objection, it has been proposed, for example, to maintain a protective layer of coke or other car bonaceous material (not containing alkali) of variable thickness, adjacent to the furnace walls, so as to prevent the plastic or semi-plastic furnace charge from coming in actual contact with the furnace wallsl themselves. So far as I am aware, however, this OFFIC-r Patented Aug. 23,1921.

and like expedients have not beenl attended .v

with satisfactory results, and, in fact, `introduce additional complicationsv interfering with the simplicity and economy of opera-` tion desirable in carrying out the process'.

It may be noted further, that the cause of;

failure, from an industrial standpoint, in many of the proposals heretofore made, has probably been due to the fact that during the operation the furnace charge shrinks to a very great extent (the amount of shrink# age, of course, depending upon the nature and proportion of the ingredients entering into the composition of the charge) and may amount to as much as one-third or more of its original volume. During this shrinking, the contents ofthe furnace become channeled and this channeling allows the nitrogen gas to pass through the furnace' charge with a corresponding diminution of the desired contact, and with a resultant low and irregular yield of the alkali metal cyanid desire( The present invention providesa mode of operation which, in overcoming the difficulties herein before referred to, supplies a satisfactory solution of the industrial or commercial problem of producing alkali metal cyanids from mixtures of the general character appropirate to that manufacture.

The accompanying drawing illustrates the preferred form of apparatus involved in the practice of the invention, the structure being shown partly in side elevation and partly n section.

Referring to the drawing, 2 represents conventionally any suitable heating furnace, provided with a grate 3, fuel charging door 4, ash pit door 5, baffles 6, and stack The details of this furnace structure may be chosen to provide the desired heating effect, and may be widely varied, as will beunderstood by those skilled in the art.

Extending through the furnace is a cylindrical metal tube 1. preferably of an alloy containing essentially nickel, chromium and iron, with or without small quantities of manganese, silicon` etc., the relative` proportions of the constituents of the alloy being such that the tube will withstand, to a satisfactory degree, the action of the fun nace gases at the required compartively high temperature. In practice, I prefer toemploy a tube of approximately l5 inches internal diameter, and of a length of about ten feet for that port-ion of the tube which traverses the heating zone of the furnace. The

upper and lower ends of the tube, outside of Iroller thrust bearings 8, on which it can be rotated, these bearings being suitably mounted to efiiciently sustain the weight imposed upon them. The angular inclination of the tubular retort may be varied more or less in accordance with the nature, both chemical and physical, of the-mixture making up the charge,--a suitable angle being, for instance the angle shown in the drawing. The upper end of the tube 1 is provided with a conveyer 13 discharging into an elbow pipe 12, whereby the retort can be fed with the furnace charge automatically, and continuously or intermittently, as may be desired. The lower end of the tubular retort is provided with a gear 9 driven by the gear 10 from the driving shaft gear 11, or the like, so as to rotate the tubular retort at the rate desired, suitable means (not shown) being provided for varying the speed of rotation.

The lower end 0f the tubular retort l is received within a stationary casing 14 closed at its upper end, suitable packing being provided, as shown at 15, to prevent the escape of gas at the joint between the stationary casing and the rotatable retort. A discharge screw 16 projects into the lower end `of the tubular retort 1; it is carried by a shaft 17 which passes through the casing 14 and is driven from any suitable source of power by the bevel gears 18. The casing 14 is provided with a discharge hopper 19 depending therefrom, and at the lower end of the hopper is' a discharge valve 20 by which the treated charge received from the retort lnay be discharged without permitting the escape of gases from the casing and without admittmg atmospheric air therethrough.

The nitrogen or nitrogen-containing gases are admitted to one end of .the tubular retort and pass through the charge therein, and the reaction gases are allowed to escape at the opposite end. In the drawing, a pipe for the inlet of the nitrogen or nitrogen-containing gases is shown at 21, connected to the stationary casing 14. At the opposite end of the tubular retort, the reaction gases maybe allowed to escape through the feeding devices for the charge, or otherwise, as

ma be desired.

n the use of the apparatus, the charge, consisting of a suitable mixture of alkali metal carbonate or alkali metal h droxid (or both) and coke, charcoal, or ot er carbonaceous material, with or without a catalyst, `such as iron, is fed into the upper part of the tubular retort l, which portion of the retort constitutes a preheating zone for the charge. From the preheating zone, the mixture passes through the reaction zone within the walls of the furnace, and thence into the cooling zone, that is to say, the lower ortion of the retort projecting beyond the urnace wall. The charge is finally withdrawn from the retort, with the assistance of the discharge screw 16, and drops into the hopper 19 from which it may be removed, as desired, by the discharge valve 20.

The operation is preferably a continuous one, the retort being maintained substantially filled with the charge throughout the operation, and the rate of discharge of the furnace charge being determined by the operation ofthe discharge screw 16. The retort, with the furnace charge therein, is rotated continuously by means of the driving gear and at the same time, the nitrogen or nitro en-containing gases are admitted to the cooling zone of the retort from the conduit 21.

The nitrogen or nitrogen-containing gases pass up through the portion of the charge in the cooling zone, and take up heat therefrom, so that the gases are pre-heated before they enter the reaction zone of the retort. So also, the temperature of the treated charge is reduced by the cooling effect of the nitrogen or nitrogen-containing gases.

Within the reaction zone of the tubular retort, the char e is tumbled by the rotation of the retort. he particles of the charge will move relatively during the introduction of nitrogen so that all of the particles are exposed thereto. The movement of the particles effectually prevents caking of the charge and adherance thereof to the walls of the retort and also prevents the formation of channels or fissures through the charge. Within this reaction zone, the charge, although reduced to a pasty or semiplastic conditlon, is thus presented to the best advantage to uniform and well distributed contact with the reaction gases, so that a correspondingly high and regular yield of alkali metal cyanid results.

The upper end of the retort, constituting the preheating zone beyond the furnace walls, being more or less filled with the incoming char e, serves as a condenser for any volatile pro uct or fume carried along out of the reaction zone, and the incoming charge is, at the same time preheated by means of the outgoing hot gases which pass through it.

As the charge shrinks in the reaction zone ofthe retort, the shrinkage is continuously and automatically taken care of by the supply of charge from the preheating zone, so that the reaction zone 1s kept completely filled. From the reaction zone, the treated charge,sti'l1 in a plastic or semi-fluid oonlbatch to be treated. The nitrogenous dition, ente'rs continuously the cooling zone, and immediately begins to solidify. In so doing, the rotation of the tubular retort causes the material to become nodulized into lumps or nodules of relatively small size, particularly appropriate to the subsequent use for which the treated charge is especially intended, that is to say, as the means for obtaining ammonia by the passage of steam therethrough or the extraction of cyanid therefrom. rl`he exit of the charge from the coolin zone is assisted and regulated, as herein efore noted, by the conveyer screw 16, which may be operated continuously or intermittently, as desired.

It will be apparent that, instead of oper ating the entire process continuously, as preferred in most cases, the apparatus is like- Wise Well adapted for operation intermittently, that is to say, by supplying it with a given amount of furnace charge, treating and discharging the same in its entirety, and then supplying its place with a succeeding gas: (Whether nitrogen per se, or a gas or mixture of gases containing nitrogen) may be obtained from any desired and suitable source as Will be Well understood by those skilled in the art.

Having thus described my invention, what I claim is: v

1. The process of producing alkali metal cyanids, which consists in filling the reaction zone of a retort with a mixture of an alkali and a carbonaceou's material, passing a nitrogenous gas through said mixture, and tumbling the mixture While subjecting it to a high heat; substantially as described.

2. The process of producing alkali metal cyanide which consists in filling the reaction Zone of a retort with a mixture of an alkali and a carbonaceous material, subjecting the reaction zone to a high heat thereby bringing the mixture in said reaction zone to a pasty condition, passing a nitrogenous gas through the mixture While causing the particles of the mixture to move relatively as the gas travels therethrough, and finally cooling and hardening the treated charge; substantially as described.

3. The process of producing alkali metal cyanids, Which consists in filling the reaction zone of an inclined tubular retort With a mixtureoi' an alkali and a carbonaceous maltion zone of an inclined tubular retort with a mixture of an alkali and a carbonaceous material, passing a nitrogenous gas through the mixture, rotating the retort on its axis While the reaction zone is subjected to a high heat, and nodulizing the treated charge by subjecting it to the nodulizing action of the discharge end of the retort beyond the reaction zone; substantially as described.

5. The process of producing alkali metal cyanide, which consists in introducing a mixture of an alkali and a carbonaceous material into the upper end of an inclined tubular retort so as to fill the reaction zone thereof, passing a nitrogenous gas through the mixture, applying a high heat to the'reaction zone of the retort so as to bring about the necessary reaction therein, while leaving a preheating zone at the upper end of the retort and a cooling zone at thelower end of the retort, and rotating the retort on its axis While the charge in the reaction zone is being subjected to the heat treatment; substantially as described.

6. The process of producing alkali metal cyanids,v which consists in introducing a mixture of an alkali and a carbonaceous materialinto the upper end of an inclined tubular retort so as to ll the reaction zone thereof, applying a high heat to the reaction zone of the retort so as to bring about the necessary reaction therein While leaving a preheating zone at the upper end of the retort and a cooling zone at the lower end of the retort, passing a nitrogenous gas through the charge in the cooling end of the retort to assist in cooling the charge therein and to become itself preheated before passing into the reaction zone, then passing said gas through the charge in the reaction zone, and rotating the retort on its axis while the charge is being subjected to the heat treatment; substantially as described.

In testimony that I claim the foregoing as my invention, I have hereunto signed my name this 15th day of March, A. D. 1918.

FLOYD J. METZGER. 

